Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds only the raw endpoint string "GET /contact_groups" and nothing about pagination defaults, ordering, or result size, so it contributes essentially no behavioral context beyond the annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two short sentences with the purpose front-loaded and no filler. The trailing "Missive: GET /contact_groups" is mildly redundant with the purpose sentence but cheap and arguably useful for API mapping.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple paginated list tool with a fully documented schema and readOnly annotations, the core information is present. The gaps are the undefined relation to missive_list_organizations and the absence of any output-shape hint (no output schema exists), which leaves the agent to infer the return structure.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so all four parameters (kind, limit, offset, contact_book) are already documented, including the kind enum. The description's phrase "within a contact book" loosely reinforces the contact_book scoping but adds no format or behavioral detail beyond the schema, matching the baseline for high coverage.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (List) and resource (contact groups/organizations) scoped to a contact book, plus the underlying endpoint. However, the sibling tool missive_list_organizations overlaps with the kind="organization" mode here, and the description never distinguishes the two, so an agent cannot fully disambiguate from the name and text alone.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives no context on when to use this tool rather than missive_list_organizations, missive_list_contact_books, or missive_list_contacts, all of which are close siblings. No prerequisites or pagination guidance are provided.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.